Thermal stability and magnetic properties of Fe-Al-Ga-P-C-B-Si amorphous thick sheets

The structure and magnetic properties of melt-spun multicomponent Fe/sub 72/Ga/sub 2/Al/sub 5/P/sub 11-x/C/sub 6/B/sub 4/Si/sub x/ (x=0-10) alloy sheets were investigated. The increases in the thermal stability and glass forming ability, and the improvement of the soft magnetic properties were recognized with the replacement of P by 1-2 at% Si. The supercooled liquid region (/spl Delta/T/sub x/) defined by the difference between crystallization temperature (T/sub x/) and glass transition temperature (T/sub g/) increases from 51 K for the Fe/sub 72/Al/sub 5/Ga/sub 2/P/sub 11/C/sub 6/B/sub 4/ alloy to 65 K for the Fe/sub 72/Al/sub 5/Ga/sub 2/P/sub 9/C/sub 6/B/sub 4/Si/sub 2/ alloy, and then decreases with increasing Si content. The maximum thickness for glass formation (t/sub max/) also increases from 140 /spl mu/m for the Fe/sub 72/Al/sub 5/Ga/sub 2/P/sub 11/C/sub 6/B/sub 4/ alloy to 190 /spl mu/m for the Fe/sub 72/Al/sub 5/Ga/sub 2/P/sub 9/C/sub 6/B/sub 4/Si/sub 2/ alloy. The increases in /spl Delta/T/sub x/ and t/sub max/ are presumably because of increased agreement with three empirical rules for glass formation. The soft magnetic properties at the thickness of over 70 /spl mu/m are also improved by the replacement of 1-2 at% Si. The magnetic properties for the Fe/sub 72/Al/sub 5/Ga/sub 2/P/sub 9/C/sub 6/B/sub 4/Si/sub 2/ amorphous alloy with the thickness of 190 /spl mu/m after optimum annealing (623 K/spl times/1.8 ks) are 169/spl times/10/sup -6/ Wbmkg/sup -1/ for saturation magnetization (/spl sigma//sub s/), 1.0 A/m for coercive force (H/sub c/), and 9000 for permeability (/spl mu//sub e/) at 1 kHz. It is therefore expected that the Fe-based amorphous alloy containing 2 at% Si is widely used as a bulk amorphous material with good soft magnetic properties.